Monolithic Multigrid for Magnetohydrodynamics

The magnetohydrodynamics (MHD) equations model a wide range of plasma physics applications and are characterized by a nonlinear system of partial differential equations that strongly couples a charged fluid with the evolution of electromagnetic fields. After discretization and linearization, the resulting system of equations is generally difficult to solve due to the coupling between variables, and the heterogeneous coefficients induced by the linearization process. In this paper, we investigate multigrid preconditioners for this system based on specialized relaxation schemes that properly address the system structure and coupling. Three extensions of Vanka relaxation are proposed and applied to problems with up to 170 million degrees of freedom and fluid and magnetic Reynolds numbers up to 400 for stationary problems and up to 20,000 for time-dependent problems

Upper Bounds on Rare K and B Decays from Minimal Flavour Violation

We study the branching ratios of rare K and B decays in models with minimal flavour violation, using the presently available information from the universal unitarity triangle analysis and from the measurements of Br(B -> X_s gamma), Br(B -> X_s l^+l^-) and Br(K^+ -> pi^+ nu nubar). We find the following upper bounds: Br(K^+ -> pi^+ nu nubar) pi^0 nu nubar)< 4.6 10^{-11}, Br(K_L -> mu mubar)_{SD} X_s nu nubar)< 5.2 10^{-5}, Br(B -> X_d nu nubar) mu mubar)< 7.4 10^{-9}, Br(B_d -> mu mubar)< 2.2 10^{-10} at 95 % probability. We analyze in detail various possible scenarios with positive or negative interference of Standard Model and New Physics contributions, and show how an improvement of experimental data corresponding to the projected 2010 B factory integrated luminosities will allow to disentangle and test these different possibilities. Finally, anticipating that subsequently the leading role in constraining this kind of new physics will be taken over by the rare decays K^+ -> pi^+ nu nubar, K_L -> pi^0 nu nubar and B_{s,d} -> mu mubar, that are dominated by the Z^0 -penguin function C, we also present plots for several branching ratios as functions of C . We point out an interesting triple correlation between K^+ -> pi^+ nu nubar, B -> X_s gamma and B -> X_s l^+l^- present in MFV models.Comment: 26 pages, 12 figure

Lifestyle travellers: Backpacking as a way of life

Scholarship on backpackers speculates some individuals may extend backpacking to a way of life. This article empirically explores this proposition using lifestyle consumption as its framing concept and conceptualises individuals who style their lives around the enduring practice of backpacking as ‘lifestyle travellers’. Ethnographic interviews with lifestyle travellers in India and Thailand offer an emic account of the practices, ideologies and social identity that characterise lifestyle travel as a distinctive subtype within backpacking. Departing from the drifter construct, which (re)constitutes this identity as socially deviant, the concept of lifestyle allows for a contemporary appraisal of these individuals’ patterns of meaningful consumption and wider insights into how ongoing mobility can lead to different ways of understanding identities and relating to place. Keywords: lifestyle consumption; backpacker; mobility; drifter; identit

Ultrasonic Flaw Detection in Turbine Rotor Component Web Geometries

Nondestructive detection of flaws in jet engine components is an essential part of assessing the integrity of the parts, and optimal design of experimental configurations is essential for high reliability detection. Due to the high cost of experimental evaluation, it would be highly desirable to accomplish this through the use of computer simulation of the detection/measurement process. This paper presents a first generation simulation model for the problem of ultrasonic detection of flaws in turbine rotor components. Included is the derivation of the model, the results of limited experimental validation of the software, and an example of its use to model the detection of penny shaped cracks in the plate-like geometry of a turbine rotor component web region

Claims of Employment Discrimination and Worker Voice

Publisher PD

Progressive cortical visual failure associated with occipital calcification and coeliac disease with relative preservation of the dorsal ‘action’ pathway

We describe the first reported case of a patient with coeliac disease and cerebral occipital calcification who shows a progressive and seemingly selective failure to recognize visual stimuli. This decline was tracked over a study period of 22 years and occurred in the absence of primary sensory or widespread intellectual impairment. Subsequent tests revealed that although the patient was unable to use shape and contour information to visually identify objects, she was nevertheless able to use this information to reach, grasp and manipulate objects under central, immediate vision. This preservation of visuo-motor control was echoed in her day-to-day ability to navigate and live at home independently. We conclude that occipital calcification following coeliac disease can lead to prominent higher visual failure that, under prescribed viewing conditions, is consistent with separable mechanisms for visual perception and action control

Role of Tobacco Use in the Etiology of Acoustic Neuroma

Two previous studies suggest that cigarette smoking reduces acoustic neuroma risk; however, an association between use of snuff tobacco and acoustic neuroma has not been investigated previously. The authors conducted a case-control study in Sweden from 2002 to 2007, in which 451 cases and 710 population-based controls completed questionnaires. Cases and controls were matched on gender, region, and age within 5 years. The authors estimated odds ratios using conditional logistic regression analyses, adjusted for education and tobacco use (snuff use in the smoking analysis and smoking in the snuff analysis). The risk of acoustic neuroma was greatly reduced in male current smokers (odds ratio (OR) = 0.41, 95% confidence interval (CI): 0.23, 0.74) and moderately reduced in female current smokers (OR = 0.70, 95% CI: 0.40, 1.23). In contrast, current snuff use among males was not associated with risk of acoustic neuroma (OR = 0.94, 95% CI: 0.57, 1.55). The authors’ findings are consistent with previous reports of lower acoustic neuroma risk among current cigarette smokers than among never smokers. The absence of an association between snuff use and acoustic neuroma suggests that some constituent of tobacco smoke other than nicotine may confer protection against acoustic neuroma

Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential

The S-wave effective range parameters of the neutron-deuteron (nd) scattering are derived in the Faddeev formalism, using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-nucleon force, yielding the observed value of the doublet scattering length and the correct differential cross sections below the deuteron breakup threshold. This conclusion is consistent with the previous result for the triton binding energy, which is nearly reproduced by fss2 without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy